It does appear to be memory-related, but as you said it's strange since you are probably only using 2 render threads, and should only need 200-400MB of cache. The rest would be available for the scene, which looks moderately complex. The high AA and reflection in the scene may be using a lot of memory, but the low render resolution should make it not as much of a problem.
Can you try the render again and 1: check "Preallocate cache" in the Renderer node and 2: watch Task Manager for overall memory use.
Also, are any of the single objects in the scene particularly large/high poly? Any large texture maps?
- Oshyan